1. Field of the Invention
The present invention relates to a semiconductor wafer, a semiconductor device, and a method of manufacturing the semiconductor device.
2. Description of the Related Art
In order to manufacture a semiconductor device such as LSI, an exposure process for exposing photo resist is needed, but among many methods, an electron beam exposure which uses an electron beam is extremely effective for attaining the refining of semiconductor devices, because it has a high resolution characteristic.
However, in order to fully bring out such a high resolution characteristic, it is necessary to carry out the alignment accurately between an electron beam exposure apparatus and a semiconductor substrate prior to the electron beam exposure. A method of this alignment is described with reference to FIG. 1.
FIG. 1 is a view showing the principle of the method of aligning an electron beam exposure apparatus with a semiconductor substrate according to a prior art.
In this method, as shown in FIG. 1, a recess with a width W1 of approximately 2 im is formed as an alignment mark 1a in a semiconductor substrate 1, and by scanning an electron beam EB on the semiconductor substrate 1, the intensity of a reflected electron EBref from the alignment mark 1a is measured by a detector 2.
The intensity of the reflected electron EBref becomes a smaller value as the height of the surface of the semiconductor substrate 1 is lower. Consequently, as shown in the lower graph 8 of FIG. 1, the intensity of the reflected electron becomes lower in the alignment mark 1a as compared with the one in the flat face of the semiconductor substrate 1, and a valley which indicates the presence of the mark 1a appears in this graph 8. Accordingly, the position of the alignment mark 1a can be grasped by detecting a valley of the graph of the intensity of the reflected electron by the detector 2, and the alignment between the semiconductor substrate 1 and the electron beam exposure apparatus is carried out based on this position.
In addition, Patent Document 1 discloses strengthening the intensity of the reflected electron from the mark by forming metal inside the alignment mark by utilizing the fact that the intensity of the reflected electron becomes strong on the surface of metal.
[Patent Document 1]
Japanese Patent Laid-Open No. Hei 6(1994)-252025